The development of microelectronics technology is promoting the upgrading of computer technology, communication technology and other electronic information technology. Therefore, microelectronics technology plays an important leading and fundamental role in the information industry revolution. Photolithography tools are indispensable for the fabrication of microelectronic devices.
In order to reduce the cost of chip manufacturing, users' demand for photolithography tools with higher yields is increasing. Driven by the market and interests, manufacturers of photolithography tools are also seeking for yield improvements. At the same time, in order to meet different needs of the market, photolithography tools are required to be able to handle wafers of various sizes.
For yield improvement of a photolithography tool, it is important to increase the yield of its wafer transfer system. Before the exposure of a wafer carried on a wafer stage has been completed, it is necessary for the wafer transfer system to get a new wafer ready to be fed onto the wafer stage. Therefore, the wafer transfer yield must be higher than the overall yield of the photolithography tool.
In general terms, the wafer transfer yield can be enhanced by 1) continuously improving the speed, acceleration, stability duration and other motion properties of a robot for wafer transfer, or 2) optimizing the configuration of the wafer transfer system, i.e., the layout of a pre-alignment apparatus, the robot and other involved components. However, currently, the manufacturers rely only on enhancement of robot motion properties for increasing the yields of their photolithography tools.